Electric circuit interrupter



' Feb. 2, 1937. R. E. BOLD ET AL 2,069,641

ELECTRIC CIRCUIT INTERRUP'IIER Filed July 26, 19:54

Inventor's Raf'ph E. Bold, Char-le R BTOWH, Lela-ho! S. Hobson,

Patented Feb. 2, 1937 UNITED STATES PATENT OFFICE ELECTRIC cmcorrmrEaaUP-mn Application July 26, 1934, Serial No. 737,064

ZClaims. (circa-146) Our invention relates to electric circuitinterrupters, more particularly to those of the heavyduty type, as oilcircuit breakers. In heavy duty operation, as for example reversingcontrol for.

steel mill apparatus, circuit interrupters are called upon not onlyemciently to make and break a power circuit but to withstand manyheavy-current interruptions without inspection or replacement of thecontact structure. Each interruption of a high intensity are results ina certain degree of burning of the contact material which is generallycoppenthereby necessitating a rugged and arc-resisting contactstructure. Furthermore, the momentary current-carrying capacity of thebreaker, as during a short circuit must be maintained at a high ratedvalue.

A principal object of our invention is the provision of an improvedcircuit interrupter of the aforesaid type which shall have highinterrupting and current-carrying capacities and be simple, rugged anddurable in construction.

Our invention will be more fully set forth in the following descriptionreferring to the accompanying drawing, and the features of novelty whichcharacterize our invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is an elevational view, partly insection, of circuit interrupter contact structure in the closed circuitposition embodying our invention; Fig. 2 is an elevational fragmentaryview of one pole of the circuit interrupter of Fig. 1 in the opencircuit position, and'Fig. 3 is an end view, partly in section, of theapparatus shown in Fig. 2.

Fig. 1 illustrates the fixed and movable contact structure of an oilcircuit breaker in the closed circuit position thereof. Thev contactstructure comprises a pair of stationary or relatively fixed contactstructures l and 2 electrically connected to the lead-in conductor studs3 and 4, respectively, of the breaker and arranged to be interconnectedin the closed circuit position by a movable conducting bridging member5. The aforesaid contact structure isimmersed in a body of suitablearc-extinguishing or insulating liquid 6 and the circuit is opened andclosed by means of an operating or lift rod 1 which is suitablyconnected to the bridging member 5 for lowering and raising the samewithin the oil body 6 with respect to the stationary contact structure.

The circuit breaker in its entirety is not ,disclosed in the interest ofclearness, and a detailed description of the same is believedunnecessary for complete understanding of the present invention otherthan to point out that the circuit breaker housing or tank may, ifdesired, be provided with structure for effecting the well known oilblast operation wherein the break atone end of the bridging member isadjacent an exhaust passage of a pressure-confining chamber in which thecontact structure isdisposed, so that arcing pressure generated at theother break is effective to direct a blast of oil through the are at thefirstnamed break.

- The stationary contact structure of each pole of the circuit breakercomprises an adapter 8 of conducting material supported by andelectrically connected to the associated conductor stud, and contactmembers which are connected to and carried by the adapter. For thepurpose of conducting heavy currents through the breaker, finger contactmembers 9 are secured to one portion of the adapter so as to be engagedand 'spread apart by a coacting wedge-shaped contact portion H! of themovable bridging member 5 as best illustrated by Fig. 3. This clearlyinvolves a wiping action tending to maintain clean the-contact surfaces.The finger contact members 9 may be of any suitable and. well knownconstruction including a pairof opposed contact portions ll electricallyconnected, as by flexible leads IE, to the adapter 8 and biased towardseach other as by leaf springs is likewise connected to the adapter 8. Inthe closed circuit position illustrated by Fig. 1, the contact portionsH are biased into good contact engagement with the opposite sides of thewedge-shaped contact portion III, with the result that high currents maytraverse the contact structure without overheating or damage to thebreaker.

In case of interruption of heavy currents we have found thatcomparatively massive butt contact structure used in conjunction withthe aforesaid flnger-type contacts above described results in greatlyimproved operation of the breaker. To this end each adapter is connectedto and sup ports a comparatively massive butt contact member Hcomprising in the present instance a blo;k of suitable contact material,as copper, which is electrically connected to the adapter as by flexiblebraided conductors l5 and is resiliently mounted with respect thereto asby compression springs Ii which are seated within sockets l1 and ID ofthe adapter and butt contact, respectively. As best illustrated by Fig.2, the butt contact I is guided for limited reciprocal movement by meansof a P ir of bars or plates", each bar being mounted in alined slots 20and 2| and having slots 22 and 23 coacting with pins 24 and 25 aflixedto the adapter and butt contact, respectively.

Referring particularly to Fig. 3, the butt contact member l 4 isprovided with a plane contact surface arranged to be engaged by a.corresponding butt contact member ZE forming an extremity of thebridging member 5. The contact portion 26 is likewise of comparativelymassive structure and may be in the form of a solid block of conductingmaterial as copper.

Upon initiation of the circuit opening movement and subsequent toseparation of the current-carrying contacts 9 and III, the butt con--tacts I 4 and 26, which serve as the arcing contacts, are maintained ingood contact engagement by the follow-up action of compression springsl5 and also by the attractive influence of the magnetic fields set up byparallel currents flowing in a generally horizontal direction throughthe large contact surfaces of the butt contacts E4 and 26. There is,therefore, no arcing at the'finger contacts, as more clearly indicatedby Fig. 3, so that the contact surfaces thereof are unimpaired for heavycurrent duty. The arcing between the buttcontacts M and 26 may beinterrupted in any suitable manner, as by the oil blast methodpreviously described.

The comparatively massive structure of the arcing contacts not onlyprovides a large heat dissipating surface but also provides an adequateamount of contact material for the arcing contacts even after a greatmany circuit interrupting operations. It will be apparent from thedrawing that the heat dissipating surface of each,

contact portion I4 and 26 is comparable to or greater than that of awedge-shaped contact In. By way of example, we have found that acircuit-interrupter embodying our invention has a contact life of theorder of approximately fifteen times longer than previous contactconstructions.

Upon closing of the circuit interrupter by upward movement of thebridging member 5, butt contacts I and 26 first engage, comprising thesprings l6, and thereby maintaining high pressure contact for carryingheavy currents from the instant of contact closing to the finalengagement of contacts 9 and I ll. i

It should be understood that our invention is not limited to specificdetails of construction and arrangement thereof herein illustrated, andthat changes and modifications may occur to one skilled in the artwithout departing from the spirit of our invention,

aoeaeu What we claim as new and desire to secure by Letters Patent ofthe United States is:

1. An electric circuit interrupter comprising a pair of fixed contacts,each of said contacts including an adapter, opposed finger contacts forcarrying heavy currents connected to said adapter, and a comparativelymassive arcing contact block mounted for lost motion with respect tosaid adapter and means including springs seated in recesses in saidadapter and block contact resiliently biasing said butt contacts awayfrom said adapter, and a movable bridging member for interconnectingsaid fixed contacts having a centrally positioned lift rod, wedge-shapedcontact portions disposed at opposite sides of said lift rod forengaging said finger contacts; and block-like arcing butt contactportions likewise massive as compared with the current carrying contactsat the extremities of said bridging member for engaging the first-namedblock contacts, said first-named butt contacts and said blocklikecontact portions each having a heat dissipating surface comparable to orgreater than that of one of said wedge-shaped contact portions, saidresilient means maintaining said block contacts in engagement subsequentto separation of said finger and wedge contact portions.

2. An electric circuit interrupter comprising a pair of fixed contacts,each of said contacts including an adapter, finger contacts for normallycarrying heavy currents connected to said adapter, an arcing contactcomprising a block massive as compared with said finger contacts,.

a pair of guide plates at opposite sides of said block connectedrespectively to said block and adapter, said plates having a pin andslot connection with respect to said adapter, a flexible conductorelectrically connecting said adapter to said block contact and meanspositioned between said guide plates resiliently biasing said blockcontact away from said adapter, and-a movable bridging member forinterconnecting said fixed contacts having a centrally positioned liftrod, wedge-shape contact portions disposed at opposite sides of saidlift rod for engaging said finger contacts, arid block-like arcing buttcontact portions likewise massive as compared with the current carryingcontacts at the extremities of said"- bridging member for engaging thefirst named block contacts.

RALPH E. BOLD. CHARLES R. BROWN. LELAND S. HOBSON.

